<html>
    <head>
        <title>
            背景色
        </title>
        <style>
     /*   
       body {
           background-image: url(tree.png);
           background-repeat: no-repeat;
           
       }*/
       #d1 {
           border: 2px solid;color: bisque; height: 300px; width: 500px; 
           border-radius: 20px;
       }

        </style>
        <body>
         <div id="div3">123</div>
         <div id="div2">456</div>
         <div id="div1">789</div>   
         <div id="d1">这是一个边框</div>
        </body>
    </head>
</html>